U.S. patent application number 12/544610 was filed with the patent office on 2010-03-11 for image pickup apparatus and image pickup control method.
This patent application is currently assigned to OLYMPUS CORPORATION. Invention is credited to Hitoshi Tsuchiya.
Application Number | 20100060748 12/544610 |
Document ID | / |
Family ID | 41798924 |
Filed Date | 2010-03-11 |
United States Patent
Application |
20100060748 |
Kind Code |
A1 |
Tsuchiya; Hitoshi |
March 11, 2010 |
IMAGE PICKUP APPARATUS AND IMAGE PICKUP CONTROL METHOD
Abstract
When an image of a subject formed by an optical system is picked
up using an image pickup device, charges obtained upon receiving
light for the subject image are accumulated with a time difference
for each scan line in the image pickup device. Concurrently, a
characteristic of the optical system is modified to change a
distance to the subject at which the image pickup device is in
focus, for each horizontal scan line.
Inventors: |
Tsuchiya; Hitoshi;
(Hamura-shi, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
OLYMPUS CORPORATION
Tokyo
JP
|
Family ID: |
41798924 |
Appl. No.: |
12/544610 |
Filed: |
August 20, 2009 |
Current U.S.
Class: |
348/222.1 ;
348/E5.031 |
Current CPC
Class: |
H04N 5/23212 20130101;
H04N 5/232939 20180801; H04N 5/3454 20130101; H04N 5/2356 20130101;
H04N 5/232933 20180801 |
Class at
Publication: |
348/222.1 ;
348/E05.031 |
International
Class: |
H04N 5/228 20060101
H04N005/228 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2008 |
JP |
2008-231264 |
Claims
1. An image pickup apparatus comprising: an image pickup device
taking and converting a subject image formed by an optical system
into a video signal; an optical adjustment section adjusting the
optical system; and a control section generating one image data
based on the video signal for the subject image captured by taking
an image of one or a plurality of consecutive first line areas on
horizontal scan lines in the image pickup device when the optical
system is subjected to a first adjustment, and the video signal for
the subject image captured by taking an image of a second line area
adjacent to the first line area when the optical system is
subjected to a second adjustment different from the first
adjustment.
2. The image pickup apparatus according to claim 1, wherein the
image pickup device performs the image taking operation with a time
difference between the first line area and the second line
area.
3. The image pickup apparatus according to claim 2, wherein the
image pickup device sets the time difference based on an exposure
time for the first line area.
4. The image pickup apparatus according to claim 2, further
comprising: a time difference changing section changing the time
difference, wherein the image pickup device performs the image
pickup operation with the time difference changed by the time
difference changing section.
5. The image pickup apparatus according to claim 1, wherein the
control section generates one image data from the video signal for
one image picked up by the image pickup device.
6. The image pickup apparatus according to claim 1, wherein the
optical adjustment section adjusts a characteristic relating to a
focus of the optical system or a focal distance of the optical
system.
7. The image pickup apparatus according to claim 1, further
comprising: a setting section setting an amount by which a lens
included in the optical system needs to move during the image
taking, wherein the control section performs the first adjustment
and the second adjustment based on the movement amount set by the
setting section.
8. The image pickup apparatus according to claim 1, wherein the
control section generates the one image data by extracting, from
the video signals for a plurality of images picked up by the image
pickup device, a video signal captured by taking an image of the
first line area corresponding to a first image and a video signal
captured by taking an image of the second line area corresponding
to a second image.
9. The image pickup apparatus according to claim 8, wherein in
taking a plurality of images, the image pickup device picks up the
first image of the subject image through the first line area and
converts the subject image into the video signal, and takes the
second image of the subject image through the second line area and
converts the subject image into the video signal.
10. The image pickup apparatus according to claim 1, wherein the
control section accumulates charges in each of the horizontal scan
lines in the image pickup device with a time difference, and moves
the optical system to vary a distance to the subject at which the
subject is in focus, for each of the horizontal scan lines to allow
image taking similar to tilt-shift image taking to be
performed.
11. The image pickup apparatus according to claim 10, wherein when
accumulation start time for a first one of the horizontal scan
lines is defined as t0, accumulation end time for a final
horizontal scan line is defined as tn, a distance between the first
horizontal scan line and the final horizontal scan line on an image
formation surface of the image pickup device is defined as L, and
an amount by which the image formation surface of the image pickup
device is moved is defined as df, the one image data is generated
which has a tilt-shift angle .theta. expressed by:
.theta.=tan.sup.-1(df/L).
12. A image pickup control method for an image pickup apparatus,
the method comprising: when an image of a subject formed by an
optical system is picked up using an image pickup device,
accumulating charges obtained upon receiving light for the subject
image, with a time difference for each scan line in the image
pickup device, and modifying a characteristic of the optical system
to change a distance to the subject at which the image pickup
device is in focus, for each horizontal scan line.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2008-231264,
filed Sep. 9, 2008, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an image pickup apparatus
taking images using perspective control without using a complicated
optical mechanism of tilt-shift lens, and an image pickup control
method for the image pickup apparatus.
[0004] 2. Description of the Related Art
[0005] What is called view cameras such as large format cameras and
medium format cameras are conventionally available. With the view
cameras, images may be taken by a technique called tilt-shift image
taking.
[0006] Images are normally taken with a positional relationship in
which the optical axis of an image taking lens is orthogonal to a
film surface. The tilt-shift image taking is an operation of
intentionally changing the positional relationship in which the
optical axis of the image taking lens is orthogonal to the film
surface. With the tilt-shift image taking, even if for example, an
image of a building is taken in such a manner that a photographer
looks up at the building, special image taking can be achieved
without causing distortion so that lower floors in the building
appear to be as large as upper floors in the building and so that
the building appears to stand straight.
[0007] For example, if an image of a train or the like is taken in
an oblique direction, the distance from the image taking position
to the head of the train is distance from the image taking position
to the trail of the train. Even in this case, the tilt-shift image
taking enables, for example, pan focus image taking in which all
positions between the head and tail of the train are in focus. It
should be noted here that a subject can be emphasized by decreasing
the depth of field to be less than that corresponding to the
optical characteristics of a lens.
[0008] For example, Jpn. Pat. Appln. KOKAI Publication No.
2005-292169 discloses a method of easily achieving image taking
based on perspective control using a common digital single-lens
reflex camera. Jpn. Pat. Appln. KOKAI Publication No. 2005-292169
includes an optical system guiding an image of a subject to an
image pickup device. The optical system includes a first adjustment
lens that is swingable around an axis of rotation orthogonal to the
optical axis of the optical system, in a direction in which the
optical axis of the lens is tilted, and a second adjustment lens
located between the first adjustment lens and the image pickup
device and which is movable in a direction orthogonal to the
optical axis of the optical system. The optical system further
includes detection means for detecting the amount by which the
first adjustment lens is tilted around the axis, appropriate-value
generation means for generating, according to the tilt amount
detected by the detection means, an appropriate position along the
orthogonal direction of the second adjustment lens at which
position the image pickup device forms the best image, second
adjustment lens moving means for moving the second adjustment lens
in a direction orthogonal to the optical axis of the second
adjustment lens, and control means for controlling the second
adjustment lens moving means to move the second adjustment lens to
the appropriate position. Thus, even when an optical path passing
through the first adjustment lens shifts, Jpn. Pat. Appln. KOKAI
Publication No. 2005-292169 allows the image pickup device to form
proper images without the need for a complicated operation.
BRIEF SUMMARY OF THE INVENTION
[0009] An image pickup apparatus according to a first aspect of the
present invention comprises an image pickup device taking and
converting a subject image formed by an optical system into a video
signal, and optical adjustment section adjusting the optical
system, and a control section generating one image data based on a
video signal for the subject image captured by taking an image of
one or a plurality of consecutive first line areas on horizontal
scan lines in the image pickup device when the optical system is
subjected to a first adjustment, and a video signal for the subject
image captured by taking an image of a second line area adjacent to
the first line area when the optical system is subjected to a
second adjustment different from the first adjustment.
[0010] An image pickup control method for an image pickup apparatus
according to a second aspect of the present invention comprises,
when an image of a subject formed by an optical system is picked up
using an image pickup device, accumulating charges obtained upon
receiving light for the subject image, with a time difference for
each horizontal scan line in the image pickup device, and modifying
a characteristic of the optical system to change a distance to the
subject at which the image pickup device is in focus, for each
horizontal scan line.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0011] FIG. 1 is a diagram showing the configuration of a digital
single-lens reflex camera as an example of an image pickup
apparatus according to a first embodiment of the present
invention;
[0012] FIG. 2 is a diagram showing the appearance of the
camera;
[0013] FIG. 3 is a schematic diagram showing horizontal scan lines
(accumulation lines) on an image formation surface of an image
sensor in the camera;
[0014] FIG. 4 is a diagram showing a temporal relationship between
charge accumulation and charge readout in the image sensor in the
camera;
[0015] FIG. 5 is a diagram showing how a focus lens or a zoom lens
group is moved when the camera is allowed to perform image taking
similar to tilt-shift image taking;
[0016] FIG. 6 is a flowchart of tilt-shift image taking showing how
the camera performs a tilt-shift image taking operation;
[0017] FIG. 7 is a diagram showing the configuration of a compact
digital camera as an example of an image pickup apparatus according
to a second embodiment of the present invention;
[0018] FIG. 8A is a front view showing the camera;
[0019] FIG. 8B is a rear view showing the camera;
[0020] FIG. 9 is a diagram showing the relationship between
accumulation and readout during image taking by CCD in the
camera;
[0021] FIG. 10 is a flowchart of tilt-shift image taking showing
how the camera performs a tilt-shift image taking operation.
DETAILED DESCRIPTION OF THE INVENTION
[0022] A first embodiment of the present invention will be
described below with reference to the drawings.
[0023] FIG. 1 is a diagram showing the configuration of a digital
single-lens reflex camera as an example of an image pickup
apparatus according to the first embodiment of the present
invention. FIG. 2 is a diagram showing the appearance of the
digital single-lens reflex camera. The present camera is composed
of an interchangeable lens 101 and a camera body 110. The
interchangeable lens 101 is provided via a camera mount provided on
the front surface of the camera body 110. The interchangeable lens
101 is made up of a focus lens 102, a zoom lens group 108, a lens
driving section 103, a lens CPU 104, a focusing mechanism 106, an
encoder 107, and a zooming mechanism 109. The focusing mechanism
106 includes a focus ring 106a. The zooming mechanism 109 includes
a zoom ring 109a.
[0024] The focus lens 102 and the zoom lens group 108 are arranged
on an optical axis P. The focus lens 102 is for focusing. The focus
lens 102 is moved in the same direction as that of the optical axis
P (the direction of arrow A) by a lens driving section 103. The
focus lens 102 moves to allow a luminous flux from a subject having
passed through the zoom lens group 108 to be formed into a subject
image on which the image pickup device 115 in a camera body 110
focuses.
[0025] The focusing mechanism 106 transmits an operation signal
corresponding to a focusing operation by a user, to the encoder
107. That is, the focusing mechanism 106 transmits the operation
signal corresponding to the user's operation of rotating the focus
ring 106a. The encoder 107 receives an operation signal from the
focusing mechanism 106 and outputs the amount of change by the
focusing operation to the lens CPU 104 as an electric signal.
[0026] The zoom lens group 108 changes focal distance. The user
operates the zooming mechanism 109 to allow the zoom lens group 108
to change the focal distance to a desired value. The zooming
mechanism 109 moves the zoom lens group 108 in the same direction
as that of the optical axis P (the direction of arrow B) in
accordance with the user's operation of rotating the zoom ring
109a. Upon receiving the user's operation, the zooming mechanism
109 moves the zoom lens group 108 in accordance with the
operation.
[0027] The lens CPU 104 counts electric signals from the encoder
107 to calculate the amount of change based on an operation
performed on the focusing mechanism 106. The lens CPU 104
communicates data to and from a system controller 118 inside the
camera body 110 via a communication connector 105. The lens CPU 104
transmits and receives various pieces of information such as camera
characteristic information and defocus amount for autofocusing as
well as various commands. The lens CPU 104 receives the amount of
change based on an operation performed on the focusing mechanism
106 and the defocus amount from the system controller 118 inside
the camera body 110, to drivingly control the lens driving section
103. The lens CPU 104 allows the lens driving section 103 to
perform driving control so as to move the focus lens 102 in the
direction of the optical axis P.
[0028] The lens driving section 103, the lens CPU 104, and the
zooming mechanism 109 make up an optical adjustment section
adjusting characteristics relating to the focus set by the focus
lens 102 serving as an optical system or characteristics relating
to the focal distance set by the zoom lens group 108.
[0029] On the other hand, the camera body 110 is made up of a main
mirror 111, a focusing screen 112, a penta prism 113, an ocular
114, an image sensor 115, a release button 116, a setting switch
117, a system controller 118, a display section 119, a memory card
120, and a shutter 121.
[0030] The main mirror 111 is rotary movable in the direction of
arrow C. During image taking, the main mirror 111 is positioned as
shown by a solid line. During image taking, the main mirror 111
retracts from the luminous flux from the subject and transmits the
subject image to the image sensor 115. During the periods other
than that of image taking, the main mirror 111 is positioned as
shown by a dashed line. During the periods other than that of image
taking, the main mirror 111 reflects the luminous flux from the
subject to form an image on a focusing screen 112.
[0031] The penta prism 113 allows the subject image formed on the
focusing screen 112 to enter the ocular 114 as an image. The ocular
114 enlarges the subject image from the penta prism 113 so that the
user can observe the subject image. Thus, the user can observe the
subject's condition through the ocular 114.
[0032] The image sensor 115 functions as an image pickup device.
The image sensor 115 takes and converts a subject image formed by
the focus lens 102 serving as an optical system and the zoom lens
group 108, into a video signal.
[0033] The release button 116 is depressed by the user to given an
instruction to start image taking.
[0034] The setting switch 117 has some switches used to set an
image taking mode, a shutter speed, and the like.
[0035] The display section 119 is made up of, for example, a liquid
crystal display. The display section 119 displays videos obtained,
information on the operation of the camera, and the like.
[0036] Image data captured by image taking is recorded in the
memory card 120.
[0037] The shutter 121 is open during image taking so as to allow
the image sensor 115 to form a subject image. While no image is
taken, the shutter is closed to prevent the luminous flux from the
subject from reaching the image sensor 115.
[0038] Now, control performed by the system controller 118 for
image taking similar to tilt-shift image taking will be
described.
[0039] The system controller 118 performs controllable focusing to
move the focus lens 102 to a first adjustment position. At this
time, an image of one or a plurality of consecutive first line
areas on horizontal scan lines (accumulation lines) on an image
formation surface of the image sensor 115 is taken to acquire a
video signal for the subject image (hereinafter referred to as a
first video signal for the subject image).
[0040] A predetermined time later, the system controller 118
performs controllable focusing to move the focus lens 102 to a
second adjustment position different from the first adjustment
position. At this time, an image of a second line area adjacent to
the first line area is taken to acquire a video signal for the
subject image (hereinafter referred to as a second video signal for
the subject image).
[0041] Then, the system controller 118 generates one image data
based on the first video signal for the subject image and the
second video signal for the subject image.
[0042] The system controller 118 controls the image taking
operation of the image sensor 115. The control allows the image
sensor 115 to perform an image taking operation with a time
difference between the first line area and the second line area on
the plurality of horizontal scan lines on the image formation
surface of the image sensor 115.
[0043] Specifically, charge accumulation and charge readout in the
image sensor 115 will be described.
[0044] FIG. 3 is a schematic diagram of horizontal scan lines
(accumulation lines) on the image formation surface of the image
sensor 115. The image formation surface of the image sensor 115 has
a plurality of horizontal scan lines S1, S2, . . . , Sn. The image
sensor 115 starts accumulating charges obtained upon receiving the
subject image, with a time difference for each of the respective
horizontal scan lines S1, S2, . . . , Sn under the control of the
system controller 118.
[0045] FIG. 4 shows an example of the temporal relationship between
the charge accumulation and charge readout in the image sensor 115.
The charge accumulation in the horizontal scan lines S1, S2, . . .
, Sn is started at time t0 for the horizontal scan line S1. The
charge accumulation in the horizontal scan line S1 lasts from time
t0 until time t2. The charge accumulation time (between time t0 and
time t2) varies with the brightness of the subject. The charge
accumulation time (between time t0 and time t2) is determined based
on a video signal from the image sensor 115.
[0046] Then, the charge accumulation in the horizontal scan line S2
is started at time t1, that is, a predetermined time (delay time)
after time t0. The time difference is determined by subtracting
time t1 from time t0. The charge accumulation in the horizontal
scan line S2 lasts from time t1 until time t3.
[0047] Then, the charge accumulation in the horizontal scan line S3
is started at time t2, that is, a predetermined time after time t1.
The time difference is the same as that between time t1 and time
t0. The charge accumulation in the horizontal scan line S3 lasts
from time t1 until time t4.
[0048] Similarly, the charge accumulation in each of the horizontal
scan lines S3, S4, . . . , Sn is started at a point in time
sequentially delayed by the delay time t1-t0 as a time
difference.
[0049] The charges accumulated in the horizontal scan lines S1, S2,
. . . , Sn are read out as follows.
[0050] At time t2, the readout of the charges accumulated in the
horizontal scan line S1 is started. The readout of the charges
accumulated in the horizontal scan line S1 is completed at time
t3.
[0051] Then, at time t3, the readout of the charges accumulated in
the horizontal scan line S2 is started. The readout of the charges
accumulated in the horizontal scan line S2 is completed at time
t4.
[0052] Then, at time t4, the readout of the charges accumulated in
the horizontal scan line S3 is started. The readout of the charges
accumulated in the horizontal scan line S3 is completed at time
t5.
[0053] Similarly, the readout of the charges accumulated in each of
the horizontal scan lines S3, S4, . . . , Sn is started at a point
in time sequentially delayed by the delay time t1-t0 as a time
difference.
[0054] The delay time t1-t0 is determined from a tilt-shift angle
described below and a driving speed for the focus lens 102 with the
minimum value of the delay time set equal to the readout time for
each of the horizontal scan lines S3, S4, . . . , Sn. In the
example shown in FIG. 4, the time required for the readout from
each of the horizontal scan lines S3, S4, . . . , Sn is equal to
the delay time t1-t0 between the horizontal scan lines S3, S4, . .
. , Sn. Thus, the delay time t1-t0 corresponds to the minimum
case.
[0055] The system controller 118 starts charge accumulation in the
respective horizontal scan lines S1, S2, . . . , Sn at the
corresponding points in time sequentially delayed by the delay time
t1-t0. Concurrently, the system controller 118 moves the focus lens
102 as shown in FIG. 5 to vary the distance to the subject at which
the subject is in focus, for each of the horizontal scan lines S1,
S2, . . . , Sn. This allows image taking similar to tilt-shift
image taking to be achieved. FIG. 5 shows a position Q observed at
time t0 before the focus lens 102 is moved and a position R
observed at time tn after the focus lens 102 has been moved.
[0056] The accumulation start time for the first horizontal scan
line S1 and the accumulation end time for the final horizontal scan
line Sn are defined as t0 and tn, respectively. As shown in FIG. 5,
the distance between the first horizontal scan line S1 and the
final scan line Sn on the image formation surface of the image
sensor 115 is denoted as L. The amount by which the image formation
surface of the image sensor 115 moves is defined as df. Then, a
tilt-shift angle .theta. can be expressed by:
.theta.=tan.sup.-1(df/L) (1)
[0057] Thus, the system controller 118 generates one image data
with the tilt-shift angle .theta. expressed by Equation (1).
[0058] When the time required to move the focus lens 102 from the
position Q to the position R is defined as Tdf, the system
controller 118 determines the delay time t1-t0 so that the
following relationship is established (time difference changing
section).
t1-t0=Tdf/n (2)
[0059] Thus, the time difference (delay time t1-t0) can be adjusted
to a predetermined value corresponding to the tilt-shift
effect.
[0060] When the time difference (delay time t1-t0) is set, the
image sensor 115 starts charge accumulation with the time
difference set for each of the horizontal scan lines S1, S2, . . .
, Sn, to perform an image taking operation.
[0061] The system controller 118 generates one image data from a
video signal for one image picked up by the image sensor 115.
[0062] The setting switch 117 is used to set the amount by which
the focus lens 102 needs to move during image taking.
[0063] The system controller 118 moves the focus lens 102 in the
direction of arrow A over time based on the movement amount of the
focus lens 102 set via the setting switch 117.
[0064] Now, the operation of tilt-shift image taking by the camera
configured as described above will be described according to the
flowchart of tilt-shift image taking shown in FIG. 6.
[0065] First, the user operates the setting switch 117 to select
the tilt-shift image taking mode. When the tilt-shift image taking
mode is selected, the system controller 118 starts a tilt-shift
image taking operation. Once the tilt-shift image taking operation
is started, the main mirror 111 is turned upward. Concurrently, the
shutter 121 is opened and the system controller 118 shifts to a
live view mode.
[0066] In the live view mode, a subject image formed by the image
sensor 115 is displayed on the display section 119 via the system
controller 118 in real time. The user operates the setting switch
117 to input the tilt-shift image taking angle .theta. while
checking the subject image displayed on the display section 119 in
real time. In step S101, the system controller 118 receives the
tilt-shift angle .theta. from the setting switch 117 to set the
angle .theta..
[0067] In step S102, the system controller 118 calculates Equation
(1) described above from the tilt-shift angle .theta. to determine
the lens driving amount by which the focus lens 102 is driven in
the direction of arrow A. The system controller 118 further
determines the driving speed for the focus lens 102.
[0068] The system controller 118 determines the driving time from
the lens driving amount and the driving speed for the focus lens
102. The system controller 118 determines the delay time t1-t0 from
the driving time based on Equation (2) described above.
[0069] Then, in step S103, the system controller 118 determines
shutter speed based on a video signal read out from the image
sensor 115. The shutter speed does not indicate the duration from
opening until closing of the shutter 121 but the duration from the
accumulation start time t0 until the accumulation end time tn in
the image sensor 115.
[0070] In the present embodiment, the image sensor 118 sets, for
example, the delay time t1-t0 for the accumulation start time for
each the horizontal scan lines S1, S2, . . . , Sn. Thus, the image
sensor 118 performs operations equivalent to those of what is
called a rolling shutter. The shutter speed is determined based on
exposure time for each of the horizontal scan lines S1, S2, . . .
Sn, the delay time t1-t0 between the horizontal scan lines S1, S2,
. . . , Sn, and the number of the horizontal scan lines S1, S2, . .
. , Sn for the image sensor 118.
[0071] When the user depresses the release button 116, then in step
S104, the system controller 118 starts controlling an image taking
operation. As described above, in the image taking operation, the
system controller 118 performs control such that charges are
accumulated with the delay time t1-t0 for each of the horizontal
scan lines S1, S2, . . . , Sn as shown in FIG. 4. Concurrently, as
shown in FIG. 5, for example, the focus lens 102 is moved at the
driving speed for the focus lens 102 determined in step S102. Thus,
the distance to the subject at which the subject is in focus varies
for each of the horizontal scan lines S1, S2, . . . , Sn. As a
result, images are taken under an effect similar to tilt-shift
image taking.
[0072] Thus, according to the above-described first embodiment, in
a normal digital single-lens reflex camera, charges are accumulated
with the delay time t2-t1 for each of the horizontal scan lines S1,
S2, . . . , Sn in the image sensor as shown in FIG. 4.
Concurrently, as shown in FIG. 5, for example, the focus lens 102
is moved to vary the distance to the subject at which the subject
is in focus, for each of the horizontal scan lines S1, S2, . . . ,
Sn. As a result, image data exhibiting an effect equivalent to
tilt-shift image taking can be captured. This enables the
configuration of a normal digital single-lens reflex camera to
exert the tilt-shift image taking effect without the need for a
particular complicated mechanism.
[0073] Image taking is performed with the focus position varied for
each of the horizontal scan lines S1, S2, . . . Sn in the image
sensor 115. Thus, the focus position varies for each of the
horizontal scan lines S1, S2, . . . Sn for the image data. This
effectively enables pan focus image taking or allows the subject to
be emphasized.
[0074] The setting switch 117 is operated to set the tilt-shift
angle .theta.. Thus, based on the set tilt-shift angle .theta., the
duration of image taking and the amount by which the focus lens 102
is adjusted are determined. The user can adjust the tilt-shift
amount according to the subject's condition.
[0075] During the tilt-shift image taking, the user turns the zoom
lens 109a as in the case of zoom burst. This allows exertion of an
effect similar to perspective control based on tilt-shift.
[0076] Now, Zoom burst will be described. Zoom burst is to operate
the zoom ring 109a to move the zoom lens 108 while the image sensor
115 is exposed, thus varying the focal distance. The zoom burst
provides a unique image in which the subject extends radially from
the center of an image taking field. This effect is exerted because
the image taking field is concurrently taken. In the present
embodiment, the image sensor 115 performs operations equivalent to
those of a rolling shutter. The focal distance varies according to
a shutter direction, thus allowing exertion of an effect similar to
perspective control based on tilt-shift.
[0077] Now, a second embodiment of the present invention will be
described.
[0078] FIG. 7 is a diagram showing the configuration of a compact
digital camera as another example of the image taking apparatus
according to the embodiment of the present invention. FIG. 8A and
FIG. 8B are diagrams showing the appearance of the compact digital
camera. FIG. 8A is a front view. FIG. 8B is a rear view.
[0079] The present camera includes a focus lens 201, a zoom lens
202, a lens driving section 203, CCD 204 as an image taking device,
a system controller 205, a release button 206, a setting switch
207, a display section 208, and a memory card 209.
[0080] The focus lens 201 moves in the same direction as that of an
optical axis P. The focus lens 201 adjusts the focus of a subject
image to be formed on CCD 204.
[0081] The zoom lens group 202 is made up of a plurality of lenses.
The zoom lens group 202 changes the focal distance to switch the
image scaling factor of the subject image to be formed on CCD
204.
[0082] The lens driving section 203 is composed of, for example, a
stepping motor. The lens driving section 203 drivingly moves the
focus lens 201 in the direction of arrow A, in the same direction
as that of the optical axis P, based on driving pulses provided by
the system controller 205. Thus, the zoom lens group 202 is moved
in the direction of arrow B, in the same direction as that of the
optical axis P.
[0083] CCD 204 converts the subject image formed through the focus
lens 201 and the zoom lens group 202 into an electric signal. CCD
204 receives control signals from the system controller 205 to read
out electric signals for the subject image as image data.
[0084] The setting switch 207 has some switches used to set an
image taking mode and various functions for the camera.
[0085] When depressed by the user, the release button 206 transmits
an image taking instruction to the system controller 205. When the
user operates the setting switch 207 while checking a menu
displayed on the display section 208, the system controller 205
determines the operation mode of the camera. When the user operates
the setting switch 207 while checking the menu displayed on the
display section 208, the system controller 205 sets the image
taking mode, the tilt-shift angle, and the like.
[0086] The display section 208 is made up of, for example, a liquid
crystal display. The display section 208 displays image taking data
and menu screens output by the system controller 205.
[0087] Image data obtained is recorded in the memory card 209.
[0088] Now, control performed by the system controller 205 for
image taking similar to tilt-shift image taking will be
described.
[0089] The system controller 205 generates one image data by
extracting, from video signals for a plurality of images picked up
by CCD 204, a video signal captured by taking an image of a first
line area corresponding to a first image and a video signal
captured by taking an image of a second line area corresponding to
a second image.
[0090] FIG. 9 shows the relationship between accumulation and
readout during image taking by CCD 204. The first charge
accumulation in CCD 204 using all horizontal scan lines K1, K2, . .
. , Kn lasts from time t0 until time t1. After the first
accumulation, charges are read out only from the horizontal scan
line K1. Readout of the charges accumulated during the first
accumulation is started at time t1.
[0091] Then, in parallel with the readout from the horizontal scan
line K1 starting at time t1, the second charge accumulation is
started using all the horizontal scan lines K1, K2, . . . , Kn in
CCD 204. The second charge accumulation lasts until time t2. After
the second accumulation, charges are read out only from the
horizontal scan line K2. Readout of the charges accumulated during
the second accumulation is started at time t2.
[0092] Similarly, each of the subsequent steps involves
accumulation using all the horizontal scan lines K1, K2, . . . , Kn
in CCD 204 and readout of accumulated charges from each of the
horizontal scan lines K3, K4, . . . , Kn.
[0093] The accumulation time t1-t0 varies with the brightness of
the subject. The accumulation time t1-t0 is determined based on the
video signal from CCD 204. The readout time needs to be shorter
than the accumulation time. Thus, the shortest accumulation time is
equal to the readout time for the horizontal scan line.
[0094] The charges are read out from each of the horizontal scan
lines K1, K2, . . . , Kn. However, the readout may be performed on
a plurality of lines at a time.
[0095] The system controller 205 reads out charges with a time
difference for each of the horizontal scan lines K1, K2, . . . , Kn
in CCD 204. Concurrently, for example, the system controller 205
moves the focus lens 201 in the direction of arrow A. Thus, the
distance to the subject at which the subject is in focus is varied
for each of the horizontal scan lines K1, K2, . . . , Kn to allow
image taking similar to tilt-shift image taking to be
performed.
[0096] The system controller 205 generates one image data by
extracting, from video signals for a plurality of images picked up
by CCD 204, a video signal captured by taking an image of a first
line area corresponding to a first image, for example, the
horizontal scan line K1, and a video signal captured by taking an
image of a second line area corresponding to a second image, for
example, the horizontal scan line K2. In this case, in taking a
plurality of images, CCD 204 takes the first image through the
first line area and converts the image into a video signal. CCD 204
then takes the second image through the second line area and
converts the image into a video signal.
[0097] Now, the operation of tilt-shift image taking by the camera
configured as described above will be described according to the
flowchart of tilt-shift image taking shown in FIG. 10.
[0098] First, the user operates the setting switch 207 to select
the tilt-shift image taking mode. When the tilt-shift image taking
mode is selected, the system controller 205 starts a tilt-shift
image taking operation. CCD 204 converts a formed subject image
into an electric signal. The system controller 205 displays the
subject image from CCD 204 on the display section 208 in real
time.
[0099] The user operates the setting switch 207 to input the
tilt-shift image taking angle .theta. while checking the subject
image displayed on the display section 208 in real time. In step
S201, the system controller 205 receives the tilt-shift angle
.theta. from the setting switch 207 to set the angle .theta..
[0100] Then, in step S202, the system controller 205 determines the
shutter speed based on the video signal output by CCD 204. The
shutter speed is determined from the accumulation time for each of
the horizontal scan lines K1, K2, . . . , Kn and the number of the
horizontal scan lines K1, K2, . . . , Kn. The shutter speed can be
reduced by adopting a scheme of reading out charges from a
plurality of lines at a time.
[0101] The system controller 205 determines, based on the set
tilt-shift angle .theta., whether the plurality of horizontal scan
lines K1, K2, . . . , Kn fall within the range of a focal depth.
Upon determining that the plurality of lines fall within the range
of the focal depth, the system controller 205 controllably
accumulates charges in a plurality of lines at a time. That is, a
larger tilt-shift angle .theta. reduces the number of the plurality
of lines that are controllable at a time. A smaller tilt-shift
angle .theta. increases the number of the plurality of lines that
are controllable at a time.
[0102] Then, in step S203, as in the case of the above-described
first embodiment, the system controller 205 calculates Equation (1)
described above based on the tilt-shift angle .theta. and the
shutter speed, corresponding to the time from the accumulation
start time t0 until the accumulation end time tn of the CCD 204, to
determine the lens driving amount by which the focus lens 201 is
driven in the direction of arrow A. The system controller 205
further determines the driving speed for the focus lens 201.
[0103] To change the focal distance, the system controller 205
determines the lens driving amount by which the zoom lens group 202
is driven in the direction of arrow B as well as the driving speed
for the zoom lens group 202. In this case, the lens driving amount
may be calculated by replacing the change amount dF of the focus
with the defocus amount df with reference to Equation (1).
[0104] Then, in step S204, the system controller 205 initializes
the number (n) of lines (n.rarw.1). Then, in step S205, the system
controller 205 starts accumulating charges in CCD 204. At this
time, charges are simultaneously accumulated in all the horizontal
scan lines K1, K2, . . . , Kn.
[0105] Then, when the charge accumulation in the horizontal scan
lines K1, K2, . . . , Kn in CCD 204 is completed, then in step
S206, the system controller 205 reads out charges accumulated in a
predetermined horizontal scan line indicated by (n). To allow the
charges accumulated in the horizontal scan lines K1, K2, . . . , Kn
to be read out, first, the readout of the charges from the
horizontal scan line K1 is started at time t1. Then, the readout of
the charges from the horizontal scan line K2 is started at time t2.
The readout of the charges from each of the horizontal scan lines
K3, K4, . . . , Kn is similarly performed following the completion
of the accumulation.
[0106] Then, in step S207, the system controller 205 adds to the
number (n) of lines (n.rarw.n+1). In this case, "1" is added to the
number (n) of lines. However, the present invention is not limited
to this aspect but any number larger than "1" may be added. For
example, if a plurality of lines are controlled at a time, the
number of these lines is added.
[0107] Then, in step S208, the system controller 205 determines
whether or not the horizontal scan line from which the charges are
read out has reached the final horizontal scan line Kn. Upon
determining that the final horizontal scan line Kn has been
reached, the system controller 205 ends the image taking.
[0108] As described above, according to the second embodiment, the
charges are read out with the time difference for each of the
horizontal scan lines K1, K2, . . . , Kn, while for example, the
focus lens 201 is moved in the direction of arrow A. Thus, the
distance to the subject is varied for each of the horizontal scan
lines K1, K2, . . . , Kn to enable image taking exhibiting an
effect equivalent to tilt-shift image taking. Consequently, the
second embodiment can exert effects similar to those of the
above-described first embodiment.
[0109] The zoom lens group 202 is moved in the direction of arrow
B. Thus, an image exhibiting an effect which is similar to
perspective control based on tilt-shift image taking and under
which the focal distance varies for each of the horizontal scan
lines K1, K2, . . . , Kn.
[0110] As described above, the present invention allows the
configuration of a normal compact digital camera to exert the
tilt-shift image taking effect without the need for a particular
complicated optical mechanism of tilt-shift lens.
[0111] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *